In the oil and gas industry it is conventional to directly or indirectly mount a rotating control device on the top of a wellhead or a blowout preventer (BOP) stack, which may include an annular blowout preventer. The rotating control device serves multiple purposes including sealing off tubulars moving in an out of a wellbore and accommodating rotation of the same. Tubulars can include a kelly, pipe or other drill string components. The rotating control device is an apparatus used for well operations and diverts fluids such as drilling mud, surface injected air or gas and produced wellbore fluids, including hydrocarbons, into a recirculating or pressure recovery mud system. Typical in-service time numbers in the tens to low hundreds of hours before some part of the operation requires service or other attention including drill bit replacement or other downhole equipment such as motors, turbines and measurement while drilling systems. It is desirable that a rotating control device last as long as other components and not be the reason operations are interrupted and result in non-productive time (NPT).
As disclosed in U.S. Pat. No. 5,662,181 to Williams et al. and U.S. Pat. No. 6,244,359 to Bridges et al., a variety of means are provided to lubricate the bearing assembly of a rotating flow head. Conventionally, most lubrication means require that a lubricant be injected or pumped into an annulus which houses the bearings to lubricate the bearings. Such lubrication means may require elaborate hydraulic mechanisms and seal arrangements to ensure adequate lubrication and cooling of the bearings. Typically, bearing assemblies are secured within the rotating flow head by means of clamps which may increase the structural height of the rotating flow head.
If the ability to maintain adequate lubrication of the bearings is compromised, the bearings will fail quickly resulting in NPT.
One of the most common sources of premature failure of bearings in current rotating control device technology is the failure of a seal or seal stack that isolates the wellbore environment from entering the bearing assembly housing.
Reducing operational NPT by maximizing the longevity of the bearings is a key objective for all companies involved in the provision of rotating control device equipment.
There is a need for structurally low profiled rotating control device which is simple and effective that maximizes the sealing function of the bearings, and prevents premature wear and failure of the rotating control device.